Two isoforms, L1and L2,ofl-amino acid oxidase have been isolated from Russell’s viper venom by Sephadex G-100 gel filtration followed by CM-Sephadex C-50 ion exchange chromatography. The enzymes, with different isoelectric points, are monomers of 60–63 kDa as observed from size exclu-sion HPLC and SDS⁄PAGE.